The genetics of intra‐ and interspecific competitive response and effect in a local population of an annual plant species

Abstract

1. While competition is recognized as a major factor responsible for plant community dynamics, the genetics of intra-and interspecific competitive ability of a target species (i.e. level of intra-population genetic variation, identity of phenotypic traits under selection and genetic bases) still deserves a deeper investigation at the local spatial scale by considering both numerous genotypes and several interacting species. 2.In this study, we tested whether the genetics of competitive response and effect in Arabidopsis thaliana was dependent on the competitive environment at both the intraspecific and interspecific levels. We used a mapping population of 48 accessions (i) that maximize the genetic diversity of a local population of A. thaliana and (ii) that have been genotyped for 168 503 single nucleotide polymorphisms. 3. In a common garden experiment, those 48 accessions were grown in six competitive environments: the absence of competition, intraspecific competition and interspecific competition with four species frequently associated with A. thaliana in natural plant communities (i.e. Poa annua, Stellaria media, Trifolium repens and Veronica arvensis). A suite of nine phenotypic traits, including a proxy of fitness, were scored on each target A. thaliana plant and the aboveground dry biomass of its corresponding competitor was estimated. 4. We first showed that crossing reaction norms of competitive response (A. thaliana performance) and effect (competitor biomass) might promote maintenance of genetic variation in a local population of A. thaliana and species coexistence at a fine spatial scale. By estimating genotypic gradients of selection, we then demonstrated that the optimal phenotypic strategies in response to competition depend on the identity of the competitor species. Finally, a genomewide association mapping approach highlighted that genomic regions associated with direct genetic effects were (i) dependent on the competitor species and (ii) different from genomic regions associated with interspecific indirect genetic effects. 5. While a first step, this study highlighted the power of adding ecology to genomics in A. thaliana to identify genetic bases underlying micro-geographic adaptation to competition. Nextgeneration sequencing technologies will undoubtedly facilitate the discovery of molecular and genetic mechanisms underlying competitive ability in other plant species, and thereby the prediction of evolutionary trajectories of plant communities.

Different sets of belowground traits predict the ability of plant species to suppress and tolerate their competitors

“…More effort should be directed towards uncovering such links. Explicit consideration of the functional traits that are associated with competitive suppression and tolerance is likely to result in better understanding of key ecological topics such as the factors governing plant community assembly (Wang et al 2010;Baron et al 2015;Kraft et al 2015), biological invasions (Suding et al 2004;Gruntman et al 2014) and response to global change (Pakeman 2011).…”

“…the ability to minimise the negative impact of sharing resources with neighbours. While some studies have reported positive correlations between competitive effect and competitive response (Novoplansky and Goldberg 2001;Wang et al 2010), others have not detected significant correlations (Cahill et al 2005;Baron et al 2015). Strong competitive effects have been linked to plant size and resource pre-emption but traits related to competitive response remain to be elucidated (Cahill et al 2005;Wang et al 2010).…”

“…competitive effect and response, respectively) or b) allow niche differentiation (demonstrated by reduced competitive suppression between species with dissimilar traits). Competitive outcome and relationships between functional traits and competitive ability may be strongly influenced by the choice of the competitor species (Wang et al 2010;Baron et al 2015). In natural conditions, community species composition and spatial structure determine the identities of interacting individuals, and the frequency of such interactions is a factor regulating local adaptation in competing species (Turkington 1989;Grondahl and Ehlers 2008;Lankau 2012;Abakumova et al 2016).…”

Natural quantitative genetic variance in plant growth differs in response to ecologically relevant temperature heterogeneity

“…Self‐fertilization is expected to reduce genetic diversity and consequently limit long‐term survival prospects of populations (reviewed in Wright, Kalisz, & Slotte, ). Yet, populations of predominantly self‐fertilizing plant species like A. thaliana and B. stricta may harbor considerable levels of local quantitative and molecular genetic variation (Baron et al., ; Kuittinen et al., ; Méndez‐Vigo et al., ; Salmela et al., ; Siemens, Haugen, Matzner, & Vanasma, ; Song et al., ; Stenøien et al., ). Because the rate at which the population mean for a quantitative trait can change is positively correlated with the amount of genetic diversity in the trait (Falconer & Mackay, ; Houle, ), understanding the maintenance of genetic variation in the wild has become one of the key questions in modern evolutionary and conservation biology (Franks et al., ; Merilä & Hendry, ).…”

“…Such phenotypic variation could be achieved for instance by genetic diversity such that different genotypes have the highest fitness in differing local environmental settings, that is, by genotype × environment interactions (Ellner & Hairston, ; Gillespie & Turelli, ; Hedrick, ), or via phenotypic plasticity of a generalist genotype (Kawecki & Ebert, ). Empirical field studies have shown that performance ranks of genotypes may change as a result of variation in inter‐ and intraspecific competition (Baron, Richirt, Villoutreix, Amsellem, & Roux, ; Shaw, Platenkamp, Shaw, & Podolsky, ) or disturbance (McLeod, Scascitelli, & Vellend, ); genotype × environment interactions in fitness have even been described on a scale of just 10 cm within a single old field (Stratton, ). In Betula pendula Roth in Finland, however, forest ground heterogeneity on a local level affected overall growth but was not sufficient to shift genotypic ranks (Mikola et al., ).…”